Iron and Leaves
Some of the monsters compelled by the Blessed Emperor to leave the Midland Sea chose to flee into the rivers and marshes that feed into the sea instead of exiting to the Iron Sea. Many of the sahuagin of the shallows moved into a region riddled by a group of mid-size rivers that were previously collectively known as the Fingers. Now they’re known as the Fangs.
The Midland Sea is supposed to be secure against sahuagin swimming beyond the shore, but a couple of ships have disappeared without any explanation, and to be on the safe side, most captains steer away from the shoreline along the Fangs.